Table 2. Some important m/z values for MS³ fragment ions from fragment A of OA and metabolites 1-4 in negative ESI mode.

	OA	1	2	3		4
Frag A	255	255	271	271	269	241 (- CO)
- H2O	237	237	253	253	251	223
- H2O	219	219	235	235	233	205
- CO2	175	175	191	191	189